Improvement in nitrogen use efficiency: Physiological and molecular approaches

Nitrogen deficiency in agricultural systems is a world-wide problem. It is true of the Indian scenario as well, The utilization efficiency of nitrogenous fertilizers under field conditions is poor. This results in loss of a costly input and accentuates the environmental degradation. In this paper, the present status of our knowledge on physiological and molecular approaches to improve nitrogen utilization efficiency at the level of its uptake, assimilation and relationship to photosynthesis, a major factor determining biomass and grain yield, is discussed. The work done in the authors' laboratory for over a decade is summarized. It is hoped that better understanding will help to apply the tools of molecular biology to genetically manipulate the crop plants so as to enhance yields at low inputs of nitrogen.